audio: Update docs on channel ordering.

include/SDL3/SDL_audio.h

@@ -43,20 +43,22 @@
  * if you aren't reading from a file) as a basic means to load sound data into
  * your program.
  *
- * For multi-channel audio, the default SDL channel mapping is:
- *
- * ```
- * 2:  FL  FR                          (stereo)
- * 3:  FL  FR LFE                      (2.1 surround)
- * 4:  FL  FR  BL  BR                  (quad)
- * 5:  FL  FR LFE  BL  BR              (4.1 surround)
- * 6:  FL  FR  FC LFE  SL  SR          (5.1 surround - last two can also be BL BR)
- * 7:  FL  FR  FC LFE  BC  SL  SR      (6.1 surround)
- * 8:  FL  FR  FC LFE  BL  BR  SL  SR  (7.1 surround)
- * ```
+ * For multi-channel audio, data is interleaved (one sample for each channel,
+ * then repeat). The SDL channel order is:
+ *
+ * - Stereo: FL, FR
+ * - 2.1 surround: FL, FR, LFE
+ * - Quad: FL, FR, BL, BR
+ * - 4.1 surround: FL, FR, LFE, BL, BR
+ * - 5.1 surround: FL, FR, FC, LFE, SL, SR (last two can also be BL BR)
+ * - 6.1 surround: FL, FR, FC, LFE, BC, SL, SR
+ * - 5.1 surround: FL, FR, FC, LFE, BL, BR, SL, SR
+ *
+ * This is the same order as DirectSound expects, but applied to all
+ * platforms; SDL will swizzle the channels as necessary if a platform
+ * expects something different.
  */
 
-
 #ifndef SDL_audio_h_
 #define SDL_audio_h_